I have struggled with this for hours now and I don't know what else to try.
I have already looked into:How to resolve : java.io.IOException: jsse.alias_no_key_entry
But no answer solved my error.
My SSL certificate was issued by Let's Encrypt and I have received all of the data as text.
I converted the text into the files: devCertificate.crt, dev.key and dev.csr
Neither using OpenSSL nor keytool to import the .key and .crt into a keystore has solved my issue.
